The invention relates to an elastic shaft plate for shaft couplings, comprising sleeves disposed angularly spaced around a shaft plate axis, said sleeves being wrapped in pairs by string coils and embedded together with the coils in an elastomeric material.
In the present context of shaft plates the sleeves are to be understood as being elongated hollow bodies or bushings of annular but not necessarily circular cross section which are open at least at one end. As compared to the elastomeric material the sleeves are made of a hard material, normally steel. The thread or string coils may consist of the most varied kinds of filaments, such as cotton or synthetic filaments or steel strings, which may be placed loosely adjacent one another or may be interlaced by knitting or weaving. The preferred suitable elastomeric material, finally, is natural or synthetic rubber or any other elastomer in which the sleeves and the string coils may be embedded, in particular by vulcanization.
In known shaft plates of the kind specified (German Pat. Nos. 408 277, 439 241, and 509 999, German Application Print No. 10 21 212, and German Utility Model No. 19 97 154) the sleeves which are wrapped in pairs by string coils are so dimensioned that they each can just receive a coupling pin. In plan view the string coils preferably are elliptical and, in addition to the sleeves, form a loop around rubber pressure plates arranged between the sleeves (German Pat. No. 509 999 and German Application Print No. 10 21 212). The elasticity of the entire shaft plate can be determined within wide limits by appropriate shaping of the pressure plates. The greater the small major axis of the ellipses formed by the string coils is as compared to the outer diameter of the sleeves, the farther the sleeves joined by a string coil may move away from each other before the string coil adopts an extended position, whereupon it can yield further only by virtue of its natural elasticity.
However, in certain cases of application, above all in couplings between a differential gear and a gear shift mechanism of a motor vehicle, the known elastic shaft plates of the kind specified display a property considered disadvantageous in that, when transmitting minor torques, they do not afford sufficient dampening of rotational oscillations of the coupled shafts unless they have relatively low torsional rigidity over the full range of admissible loads. This means that at the maximum permissible torque load such shaft plates have a great torsional angle and store a correspondingly large amount of mechanical energy. In consequence of this property known as the "wind-up effect" such shaft plates pass on the energy stored in them to the driven shaft at relatively little dampening when the torque transmitted diminishes. In the case of motor vehicles this may lead to undesired pitching motions.
Therefore, it is an object of the present invention to provide an elastic shaft plate of the kind specified which is distinguished not only by a high specific loading capacity but also by particularly favorable dampening properties and good elasticity in the range of minor or medium torque loads and which, at the same time, avoids the disturbing wind-up effect at higher torque loads.